HTTP文件下载

                FileInfo fi = new FileInfo(FilePath);
                HttpResponse contextResponse = System.Web.HttpContext.Current.Response;
                contextResponse.Clear();
                contextResponse.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode("FileName", System.Text.Encoding.UTF8));
                contextResponse.AddHeader("Content-Length",fi.Length.ToString());
                contextResponse.ContentType = "application/octet-stream";
                contextResponse.Filter.Close();
                contextResponse.WriteFile(fi.FullName);
                contextResponse.End();
                contextResponse.Flush();